Query Options & Results

The DotNetToolkit.Repository supports fetch query strategy, specification query strategy and even pagination when it comes to fetching data. These strategies can be setup using the QueryOptions and the data is returned as a PagedQueryResult.

In cases where you need to fetch navigation properties (like entity framework QueryableExtensions.Include for example), you would want to use what's called a FetchQueryStrategy object. For cases where you need to filter the data that is being fetched, then you would use what's called a SpecificationQueryStrategy object. Each of these strategies can be used as part of the QueryOptions.

Whenever the repository uses a QueryOptions, in most cases, a PagedQueryResult is returned. The PagedQueryResult holds the result that was returned as well as the total number of rows from the database (this information is most cases is obtained in a single select query statement, and can be helpful when doing pagination and need to know the original total count before pagination is applied).

Fetching Strategy

// **** Define a default fetching strategy ****

var fetchStrategy = new FetchQueryStrategy<Customer>()
  .Fetch(x => x.CustomerAddress)
  .Fetch(x => x.CustomerPhone); // Include multiple navigation properties this way

// **** Define the query options contaning the strategy ****

var queryOptions = new QueryOptions<Customer>()
  .Include(fetchStrategy) // This will include the fetching strategy in the query options
  .Include(new FetchQueryStrategy<Customer>().Fetch(x => x.CustomerOrder)); // Multiple fetching strategies can be combined this way

// **** You can also fetch properties with the query options object itself ****

queryOptions = new QueryOptions<Customer>()
  .Fetch(x => x.CustomerAddress)
  .Fetch(x => x.CustomerPhone); // Include multiple navigation properties this way

// **** Gets the query result ****

var queryResult = repo.FindAll(queryOptions);

Specification Strategy

// **** Define a default specification strategy with a predicate which is used to filter the data ****

var spec = new SpecificationQueryStrategy<Customer>(x => x.Name = "Random Name");

// **** You can also combine specifications and predicate expressions ****

var combinedSpec = spec
  .And(new SpecificationQueryStrategy<Customer>(x => x.Id > 100)) // Combine using a spec
  .Or(x => x.Id == 1); // Combine using a predicate expression

// **** Define the query options contaning the strategy to filter the data ****

var queryOptions = new QueryOptions<Customer>()
  .Include(spec) // This will include the specification strategy in the query options
  .Include(new SpecificationQueryStrategy<Customer>(x => x.Id > 100)); // Multiple specs can be combined this way

// **** You can also set a specification expression predicate on the query options object itself ****

queryOptions = new QueryOptions<Customer>()
  .SatisfyBy(x => x.Name = "Random Name")
  .SatisfyBy(x => x.Id > 100); // Multiple specification expression predicates can be combined this way

// **** Gets the query result ****

var queryResult = repo.FindAll(queryOptions);

Pagination

// **** You can page the data using the query options ****

var queryOptions = new QueryOptions<Customer>()
  .Page(pageIndex: 1) // Using a paging index (and a default page size of 100 items)
  .Page(pageIndex: 1, pageSize: 10); // Page with explicit index and page size

// **** Gets the query result ****

var queryResult = repo.FindAll(queryOptions);

Sorting

// **** You can sort the data using the query options ****

var queryOptions = new QueryOptions<Customer>()
  .OrderBy(x => x.Id) // Ascending sort
  .OrderByDescending(x => x.Name); // Descending sort - Multiple sorting properties can be applied this way

// **** Gets the query result ****

var queryResult = repo.FindAll(queryOptions);